1. Field of the Invention
The present invention is directed generally to methods and apparatus for enhancing the production of petroleum products from existing wells, especially wells that have become somewhat depleted or wells that require lateral passages extending into the surrounding formation for stimulation of efficient production. More particularly, the present invention concerns methods and apparatus for single run cutting or milling a section of well casing from the casing string of an existing well to form a casing interval, precisely locating lateral passage forming apparatus with respect to the casing interval and forming one or more lateral passages that extend from the casing interval a considerable distance into the surrounding subsurface production formation that is intersected by the wellbore. More specifically, the present invention concerns a method and apparatus for accomplishing, in a single run or trip of equipment into a wellbore, a casing cutting or milling operation to form a casing interval exposing the surrounding formation, positioning of lateral production passage forming apparatus and jetting or otherwise forming one or more lateral passages from the casing interval into the formation.
2. Description of the Prior Art
Many wells have been drilled for production of petroleum products over the years and many of these wells have ceased efficient production due to a variety of reasons. Typically wells are drilled and as part of the drilling process the wells are lined with well casing that is cemented to the formation. Completion of the wells is typically accomplished by perforating the casing via the use of explosive well perforation charges. In later years the production of such wells has been stimulated by drilling, milling or cutting openings in the casing and then landing and orienting lateral passage drilling or jetting tools at a designated depth for generating lateral passages into the surrounding formation. Typically a landing tool is run into the well casing and is secured at a desired depth in relation to the depth of the formation of interest. Then a casing milling or casing cutting tool is run into the well casing to the desired depth, is landed on the landing tool in properly oriented position and is activated to mill an opening or cut an interval in the well casing so as to expose the surrounding production formation. The casing milling or cutting tool is then pulled from the well casing and a lateral passage drilling or jetting tool is run into the casing string and is landed on the landing tool and secured in place. The lateral passage drilling or jetting tool is then activated to form one or more lateral passages that extend from the casing opening or casing interval to a desired depth within the formation. These lateral passages typically enhance the collection and production of petroleum products from the formation.
The potential for stimulating well production by forming lateral passages should be accomplished by minimal well service time and at minimal cost; otherwise the cost of achieving enhanced well production, from the standpoint of labor, material and equipment, could far exceed the benefit to the operator of the well. It is desirable therefore to minimize service costs by achieving casing milling or cutting and lateral passage formation by running into the casing a tool that has the capability of effectively performing both operations in a single run or trip so that labor and machinery costs can be as low as possible.
Existing casing cutting or milling products found in the marketplace include section mills which cut a section of casing in a well. Other casing cutter products that are presently available in the well servicing industry include devices which contain blades that are provided on outwardly moving arms to cut a section of well casing when the arms are rotated. These arms are typically moved outwardly by the flow of fluid pumped through a tubular work string from fluid pumps that are components of the surface equipment. Other casing cutter mechanisms of the petroleum industry include mills which are actuated to cut a rectangular opening or window in the casing to allow the lateral exit movement of a drill bit from a drilling tool for drilling a lateral passage into the formation. Similar types of lateral passage tools include jetting hoses and nozzles that are directed laterally into the formation simultaneously with directing a high pressure jet of fluid against the formation to blast or erode a lateral passage extending from the wellbore into the surrounding production formation.
Casing cutting devices have been developed and used which include devices employing high pressure water to cut a section of casing or which use abrasive fluids to cut, erode or blast away a section of casing to develop a hole in the casing that exposes the surrounding earth formation. It is obvious that existing products and techniques using abrasive materials in the fluid for the purpose of jet blasting or erosion of the well casing can be very damaging to the surface equipment, such as pumps, valves, fluid handling conduits and the like, thus requiring significant equipment maintenance, repair and replacement for casing interval cutting operations or casing window cutting operations. Also, it is known that existing products and techniques employing high pressure jet drills can create damage to the surface and conveyance equipment, thus adding to the cost and adversely affecting the commercial viability of subsurface lateral passage formation techniques.
Some casing cutter devices that are available to the petroleum production industry at the present time may cut a casing interval from the bottom up, i.e., penetrating the well casing wall in a casing cutting operation and then moving the cutting elements upwardly from the point of casing penetration to cut away a section of casing and form a casing interval from which lateral bores or passages may be subsequently formed by separate drilling or jetting operations. These types of casing cutter typically develop an uneven, perhaps jagged upwardly facing annular shoulder on the casing that remains below the casing interval. If this annular shoulder is to be employed to enable precision landing and positioning of other well service equipment, it can be quite difficult to achieve the degree of landing and positioning accuracy that is needed.
Casing cutting systems have also been developed which employ drills that cut a single hole in the well casing wall for the purpose of installing a lateral borehole by a jetting process. The casing opening or window drilling apparatus is employed for the single purpose of forming a hole of desired diameter in the well casing, after which the drilling apparatus is retrieved from the well. Lateral passage drilling or jetting apparatus is then run into the well to the desired depth and is activated to form a single lateral passage into the surrounding formation. This process necessitates running different equipment into a well casing, multiple times to form multiple lateral passages that radiate into the formation from the well casing, thus significantly adding to the service time and cost of lateral passage formation and perhaps failing to achieve the commercial viability of the well servicing operation.
A problem with existing products and techniques for lateral passage formation is that they require significant surface equipment at the surface of the well site to operate the various types of equipment that are required to cut a section of casing. These existing casing cutting and lateral passage forming systems require additional trips of equipment into and out of the well casing to cut a section of casing and then to land and orient a deflector device to install lateral boreholes. Casing cutting systems that are in use at the present time generally cut from the bottom up, which does not leave a clean ledge on the lower end of the section or interval cut. The cutters of these types of devices are extended from a casing cutting tool and then moved laterally or pivotally into and through the wall of the casing. This method of cutting a well casing can develop an irregular upwardly facing shoulder on the casing below the interval that is cut. This irregular upwardly facing annular shoulder can adversely affect the precision that is needed for landing equipment at the interval and preparing that equipment for subsequent jetting or drilling operations to form the desired lateral passages.
Another problem with existing casing cutting systems and techniques is that it may require several well servicing trips to enable running, landing and positioning of the desired equipment to cut a section of casing and then to subsequently accurately land a deflector device in oriented position relative to the casing interval for drilling or jetting formation of the lateral boreholes from the casing interval into the formation.